Industrial processes or operating-water systems, such as open or closed water-cycle systems, offer suitable conditions for the growth of microorganisms. Industrial processes include, but are not limited to, oil and natural gas systems and their down-hole applications and cooling water systems. Other examples of industrial systems are those systems that are found in the food and beverage industries. These water systems may form a harbor or reservoir that perpetuates growth of pathogenic microorganisms such as Legionella pneumophila, Pseudomonas aeruginosa, sulfate reducing bacteria, and other microbial fouling pathogens.
Many of these microorganisms form a slime known as biofilm on the surfaces of water-bearing systems. The biofilms offer a selective advantage to microorganisms to ensure the microorganisms' survival or to allow them a certain time to exist in a dormant state until suitable growth conditions arise. In the case of cooling water systems in particular, these biofilm deposits can lead to reduced heat exchange efficiency, pipeline damage, and corrosion within the systems. Adverse effects on process control are possible, which can ultimately reduce the efficiency of the industrial process in question and impair product quality. In addition, biofilm or slime deposits generally lead to higher energy consumption.
Control of biofilms involves the prevention of microbial attachment and the removal of existing bio-films from surfaces. While removal in many contexts is accomplished by short cleansing treatments with highly caustic or oxidizing or non-oxidizing agents, the most commonly used materials to control bio-films are biocides and biodispersants.
The deposition of the bacterial slimes may be controlled with biocides that kill off the microorganisms in the operating water and thus prevent slime production. Due to the protective nature of biofilms, however, larger concentrations are needed to penetrate the biofilm and kill the microorganisms within. Thus, biocides to control biofilm increase costs, and because of their toxicity, biocides pose considerable dangers to those handling them and to the environment.
Surfactants are also regularly applied in water treatment programs as biodispersant agents believed to play a role in the removal of organic masses from surfaces. Surfactants may also enhance biocide efficacy or assist in the water miscibility of various biocidal agents. Unfortunately, some surfactants are toxic to non-target aquatic organisms upon discharge to common receiving bodies of water or possess functional groups that have the potential to generate AOX species, such as amines and amides, and are currently regulated in European countries.
The more non-toxic surfactants often require higher levels of concentrations to achieve their purpose, thereby making them uneconomical due to the huge amount of water treated, and prone to forming high levels of unwanted foam. Foaming results in the need to feed antifoam compositions to the system. Foam, even with feeding antifoam compositions, may be problematic in some industrial applications like air separation processes.
Additionally, in many aqueous systems, such as in industrial cooling systems, scale control agents (“SCA”) are added to the system water to inhibit or control scale formation that would otherwise form. Such scale forming precipitates include calcium, magnesium, and iron or copper salts and complexes. In many cases in which biofilm control agents are also added to these systems, the biofilm control agent impairs the ability of the SCA to remain dissolved or suspended in the water system. Undesirable precipitation of the SCA means that less of the SCA is available in the system water to perform its intended scale control function.